Within the packaging industry, there is a progressive change towards the use of containers of plastic material. This relates to both containers for beverages, including carbonated beverages, and containers for foods. As far as foods are concerned, there is an express desire in the art also to be able to employ containers of plastic material for the storage of preserved foods. In all of these fields of application, the insufficient barrier properties of the plastic material—and in particular its insufficient capacity to prevent the passage of gases, for example oxygen and CO2, vaporized liquids such as water vapor etc. entail that the shelf-life and durability of the products stored in the containers will be far too short.
A number of proposals have been put forward in the art to solve the above problem, but the proposed techniques have failed to meet established demands of cost in combination with barrier properties in order that containers of plastic material may successfully be employed within the above-outlined sectors. Examples of solutions proposed in the art include:                laminates in which two or more layers of plastic material are combined with one another and in which the material in each layer possesses properties which entail that, for instance, gas penetration, light penetration or moisture penetration are reduced;        constructions in which, for example, a metal such as aluminum is encapsulated between the plastic materials or, for instance, forms the inner surface of the container; and        constructions in which a barrier material other than metal is applied interiorly or in layers between the plastic material.Solutions are also known in the art in which plastic materials of different types are mixed and thereafter molded to form containers. Thus, for example, it is previously known to produce containers of plastic material in which the plastic material consists of a mixture of polyethylene terephthalate (PET) and polyamide. See, e.g., U.S. Pat. Nos. 5,034,252; 5,281,360; 5,641,825; and 5,759,653. It is also previously known to produce containers of plastic material in which the plastic material consists of a mixture containing EVOH. See, e.g., U.S. Pat. Nos. 4,952,628; 5,194,306; 5,110,855; 5,069,946; and 4,971,864. Unfortunately, these attempts have yielded commercially unsatisfactory results.        
Barrier layers that consist essentially of EVOH have also been tried for bottle applications. These attempts, unfortunately, suffer from several disadvantages. For example, barrier layers made from pure EVOH are relatively expensive (typically the cost for EVOH is about three times that for PET). In addition, the adhesion of a pure EVOH barrier layer to adjacent PET layers is quite poor. Moreover, it is known that EVOH barriers are quite moisture sensitive (e.g., at low humidity the barrier properties of EVOH are good, while at high humidity the barrier properties degrade substantially). Consequently, EVOH barriers have not achieved widespread commercial acceptance for bottle applications.
From the foregoing, it will be appreciated that what is needed in the art is improved plastic containers having even greater barrier properties for gases such as oxygen and CO2. Such containers and materials and methods for preparing the same are disclosed and claimed herein.